Process for adjusting WVTR and other properties of a polyolefin film

ABSTRACT

A process for rendering films, film composites, and articles made therefrom less resistant to passage of water vapor by passing a filled precursor film or film composite through the nip of interdigitating grooved rollers. The films or film composites are generally formed using a precursor film of a film forming polyolefin or polyolefin blend, with a relatively high filler loading and optionally an elastomer. A process is disclosed for making diapers or other disposable items where a relatively high water vapor is coupled with a resistance to liquid strikethrough. In one embodiment of the invention, the interdigitating grooved rollers are maintained in a temperature range of from about 91° F. to about 159° F.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part application ofco-pending U.S. Application No. 08/690,136 filed Jul. 31, 1996. Thisapplication claims the benefit of U.S. Provisional Application Nos.60/104,452 and 60/104,455 filed Oct. 16, 1998 and U.S. ProvisionalApplication Nos. 60/104,948 and 60/104,985 filed Oct. 20, 1998.

TECHNICAL FIELD

[0002] This invention relates generally a process of adjusting the watervapor transmission/porosity of films and film composites, whilemaintaining general resistance to liquid transmission (strikethrough).More specifically this invention is directed towards a process forproducing films, film composites, and articles made therefrom, that aremade permeable to water vapor, by passing them through interdigitatinggrooved rollers. Also, more specifically this invention is directedtoward filled polypropylene films having excellent Water VaporTransmission Rates (WVTR), high tear strength, high dart impactstrength, and a soft feel.

BACKGROUND OF THE INVENTION

[0003] Polyolefin films which are rendered more permeable to water vaporusing filler loading and orientation are known.

[0004] Such films or film composites are said to be more breathable,that is to have improved, increased permeability to water vapors, whilemaintaining a resistance to liquid strikethrough (defined herein). Usesof such films or film composites include on a diaper the permeability ofwhich may permit the passage of moisture vapor and air, whilesubstantially preventing the passage of liquid. The advantages of such afilm used in a diaper are that after the wearer voids, the liquid isgenerally retained, while much of the liquid vapor can escape decreasingthe “wet feeling”, and lowering the possibility of uncomfortable diaperrash.

[0005] Interdigitating grooved rollers have been used to orient eithercertain films or exclusively nonwoven laminates. Use of such rollers toorient (i.e., stretch) a film or nonwoven substrate is typicallyreferred to as a ring-rolling process. To increase the water vaportransmission rate (“WVTR”) of a film stretched by a ring-rollingprocess, it has been customary to increase either the filler loading inthe formulation or the depth of engagement of the interdigitatinggrooves. However, both of these processing options have technicallimitations on their ability to increase the WVTR of a film. Also, eachoption can potentially have negative effects on the physical propertiesof the stretched film, if a specific film's tolerance for filler loadingand/or groove engagement depth is exceeded. Accordingly, there is a needfor alternative means for increasing the WVTR, without negativelyeffecting a film's physical properties.

[0006] Also, it is desired for many applications of breathable films,such as disposable diapers, adult incontinent products, and femininehygiene devices, to produce a film appearance that can provide themanufacturer and consumers of such products visual evidence of thoseproducts made of breathable films versus those made from non-breathablefilms.

[0007] U.S. Pat. No. 4,472,328, assigned to Mitsubishi ChemicalIndustries, Ltd., suggests a breathable polyolefin film prepared from apolyolefin/filler composition having from 20 percent to 80 percent byweight of a filler such as a surface treated calcium carbonate. A liquidor waxy hydrocarbon polymer elastomer such as a hydroxyl-terminatedliquid polybutadiene was purported to produce a precursor film thatcould be mono-axially or biaxially stretched to make a film breathable.The breathable film described by Mitsubishi is also described in GreatBritain Patent No.2,115,702, assigned to Kao Corporation. The Kao patentfurther describes a disposable diaper prepared with a breathable film asdisclosed by the Mitsubishi patent. The breathable film is used as abacking for the diaper to contain liquid.

[0008] U.S. Pat. No. 4,350,655 by W. H. Hoge, assigned to Biax FiberFilm, describes a porous polyolefin synthetic paper film containing atleast 50 percent by weight of a coated inorganic filler. The filmcomposition was comprised of from 50 to 70 weight percent of aninorganic filler material coated with a silicon or titanium fatty acidester. To produce such a film product, Hoge teaches to cool thedisclosed film substrate down into a temperature range of 10° C. to 70°C. (i.e., 50° F. to 158° F., respectively) prior to stretching the film.Hoge refers to such a process as a “cold stretching” the film. Hoge alsoindicates that such cold stretching helps develop the desired voidvolume and surface ruptures per unit area so that weight percent resincontent of the final product ranges from 0.18 to about 0.32 g/cm³.Moreover, the precursor film is formed without the addition of anelastomer and contains an inorganic filler surface coated with either aSi or Ti fatty acid ester. Some of the resulting films were stated to beboth vapor and liquid permeable, however, at least one film (Example 3)was stated to be permeable to air.

[0009] U.S. Pat. No. 4,777,073 (Sheth) suggests a breathable filmproduced by stretching of a precursor film prepared from apolyolefin/filler composition. Sheth suggests that the permeability andstrength, especially tear strength are improved by melt embossing theprecursor film with a patterned melt embossing roller and stretching thefilm to impart a pattern of different film thickness having greaterpermeability within the areas of reduced thickness compared to the areasof greater thickness.

[0010] Most of these techniques require that a film or film composite berendered breathable, regardless of the technique but generally throughtentering (for transverse direction or TD orientation, and differentialspeeds of two rollers for machine direction or MD orientation), in aseparate operation, prior to final construction of the end-use article,for instance the diaper, leading to expensive double processing or moreexpensive transport of the film rendered less dense by the tenteringoperation.

[0011] Among the most serious limitations, is the extreme difficulty inproducing a cost effective lamination between polypropylene nonwovenmaterials and polyethylene breathable films. Traditional glue, hotmelt,or meltblown adhesive techniques can be used, but require the additionalcost and process complexity of the gluing system and the adhesive. Thepreferred method of heat lamination was generally not reliable becausethe difference in melting points of the polypropylene nonwoven (˜16120C.) and the polyethylene film (˜125° C.). To achieve an adequatelamination bond strength between the two materials, pin holes or damageto the breathable film at the film/nonwoven bond site resulted.

[0012] Previous polypropylene breathable films, while having laminationadvantages over polyethylene films, have been deficient in a number ofother performance categories. Film oriented by traditional MachineDirection Orientation, Transverse Direction Orientation, or BiaxialOrientation (all known in the art) have had very low tear and impactstrength.

[0013] For those product applications which do not laminate thebreathable film directly to a nonwoven, or which by nature of theproduct, a hot melt type adhesive gluing system is desirable (such as abreathable film diaper backsheet), polypropylene breathable film will bemore resistant to glue burn through of the film. Thus, the use of apolypropylene breathable film helps to achieve product integrity. Also,the use of higher temperature glues, as well as a lower quantity of glueis required for adequate product bond strength.

[0014] Accordingly, there is need for an improved ring-rolling processand/or polymer film composition that can increase the WVTR of a film,without significantly diminishing the film's physical properties. Thereis also a commercial need for a polypropylene microporous breathablefilm with high tear and impact strengths well as a soft feel. Also,there is need for films produced by such an improved process to bereadily distinguishable as breathable films.

SUMMARY OF THE INVENTION

[0015] According to one aspect of the present invention, there isprovided a process for producing a film having a WVTR greater than 200g/m²/day at 38° C. and 90% relative humidity comprising a polyolefin anda filler, said process comprising: a) extruding a precursor film fromsaid polyolefin blend comprising said first and said second polymercompositions and said filler, said filler concentration being in a rangeof from about 16.5 to about 71.5 wt. %; and b) passing said precursorfilm between at least one pair of interdigitating grooved rollers, saidrollers being maintained in a temperature range from about 91° F. toabout 159° F., so that said film is heated to produce said film having aWVTR greater than 200 g/m²/day at 38° C. and 90% relative humidity.

[0016] According to another aspect of the present invention, there isprovided a process for producing a film having a WVTR of at least 200g/m²/day at 38° C. and 90% relative humidity comprising a polyolefinblend, said polyolefin blend having at least a first and a secondpolymer composition, and a filler, said process comprising: a) extrudinga precursor film from said polyolefin blend comprising said first andsaid second polymer compositions and said filler, said fillerconcentration being in a range of from about 16.5 to about 71.5 wt. %,wherein, i) said first polymer composition is a polypropylene and ii)said second polymer composition is selected from the group consisting ofelastomers, plastomers, styrenic block copolymers, ethylene-maleicanhydride copolymers, ethylene ethyl acetate, and combinations thereof,and b) passing said precursor film between at least one pair ofinterdigitating grooved rollers so that said film has at least: i) aWVTR in a range of from about 200 g/m²/day to about 10,000 g/m²/day at38° C. and 90% relative humidity, ii) a dart drop impact in a range offrom about 100 grams to about 300 grams, and iii) an elongation selectedfrom the group consisting of machine direction, transverse direction andcombinations thereof in a range of from about 150% to about 550%.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The foregoing aspects, features and advantages of the presentinvention will become clearer and more fully understood when thefollowing detailed description, and appended claims are read inconjunction with the accompanying drawings, in which is a schematicdrawing of an embodiment of our invention for imparting breathability toa film or film composite:

[0018]FIG. 1 is a schematic view of a process for converting a precursorfilm (and optionally other layers) into a film with greater WVTR;

[0019]FIG. 2 illustrates a cross-sectional view of the interdigitatinggrooved rollers of FIG. 1, taken along the lines 2-2;

[0020]FIG. 3 illustrates an enlarged view of area 3 from FIG. 2 showingseveral interdigitating teeth from the grooved rollers; and

[0021]FIG. 4 shows how a film is stretched with interdigitating rollers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0022] We have discovered that certain polyolefin films and filmcomposites can be processed to have greater water vapor transmissionrates, relatively low liquid strikethrough, while maintaining filmintegrity, by using certain film forming formulations and techniques andpassing the film, the film composite and/or the finished fabricateddisposable article, through a nip of at least one pair ofinterdigitating grooved rollers.

[0023] We have discovered that applying heat to interdigitating groovedrollers results in a substantial improvement in orientationeffectiveness (WVTR increases), and imparts a 3 dimensionality to thefilm which differentiates it from other breathable film. In addition anew control is provided for the adjustment of film breathability, i.e.rather than require a formulation change, or adjustment to the depth ofactivation, to control WVTR levels, roller temperature merely needs tobe adjusted. As can be seen from the following examples, with all otherfactors constant, an increase in interdigitating roll temperature from70° F. to 140° F., increases WVTR from 1900 g/m²/day to 4100 g/m²/day.

[0024] We have also discovered that producing a precursor film from apolypropylene and filler (preferably calcium carbonate) blend, thenincrementally orienting the film with interdigitating grooved rollers inthe machine direction, or the transverse direction, or both, will yielda reasonably soft film (to the touch) with good impact and tearstrength. It was further discovered that by adding a minority amount oflow density polyethylene, extrusion processability was greatly improved.It was further discovered that the addition of a minority amount of anelastomer or plastomer improved impact and tear strength further, andcontributed to an even softer film “feel”. Impact strength isapproximately double that of previously available polypropylenebreathable films stretched by conventional techniques, other thaninterdigitating grooved rollers. MD tear strength is more than triplethat of Machine Direction Oriented and Biaxial Oriented polypropylenebreathable films. TD tear strength is greater than triple that ofTransverse Direction Oriented and Biaxial Oriented polypropylenebreathable films. Because stretching such film blends by interdigitatinggrooved rollers was expected to produce film with substantially similarphysical properties as films with stretched with conventional stretchingtechniques, such dramatic improvements in physical properties provedmost surprising.

[0025] In certain embodiments of the invention, a polyolefin film orfilm composite comprises at least one layer of a disposable article andis rendered breathable by passing the film, film composite or fabricatedarticle through interdigitating grooved rollers. The film, filmcomposite or fabricated article will have either a single layer ormultilayer construction and the polyolefin/filler combination can beco-extruded, laminated or blended with other polymers or polymer basedfabricated articles.

[0026] In an embodiment of the invention, a film (“precursor film”) ismade, utilizing a polyolefin or a polyolefin blend with a relativelyhigher filler loading, generally including embossing a patternthereupon, such that its subsequent manipulation, either by itself, in afilm composite or as a part of a disposable article, will render thefilm breathable (hereinafter defined as water vapor permeable, withincertain limits of WVTR, while maintaining a certain level of liquidimpermeability) while maintaining a minimum level of physicalproperties, elongation/tensile strength being of most importance. Themanipulation of the film, film composite, and/or fabricated disposablearticle includes passing all or parts of the film, film composite,and/or fabricated disposable article through a grooved roller and/orinterdigitating grooved rollers, at a rate sufficient to develop aminimum level of breathability to the film or film portion of thearticle, at a commercial and economical rate.

[0027] The tear strength, elasticity, and softness of a film preparedfrom the polyolefin/filler composition may be improved by addition ofsmall amounts of an olefinic elastomer.

[0028] The WVTR desired is above 100 g/m²/day @ 38° C., 90% RH (RelativeHumidity), preferably above 200 g/m²/day, and can be easily greater than1000 g/m²/day.

Introduction

[0029] This invention concerns all polyolefin/filler based breathablefilms that have high WVTR, the ability to be drawn down to low basisweights, and methods for making same. Particularly useful in these filmsand methods are impact copolymer polypropylene. The process is alsoeffective for all polyolefin materials. The term impact copolymer hereinrefers to a homopolymer matrix having a small amount of anethylene/propylene copolymer dispersed throughout.

[0030] This invention further includes certain polyolefins, theirconversion into fabricated articles such as films, articles made fromsuch films, and applications in which such articles having high WVTRcombined with good physical properties are desirable. The resultingfilms, and film composites, (including co-extruded and laminated films)have combinations of properties rendering them superior and unique tofilms or film composites previously available. The films disclosedherein are particularly well suited for use in producing certain classesof high WVTR films, consumer and industrial articles using the films incombination with for instance, polymeric woven or non-woven materials.Such consumer articles include, but are not limited to diapers, adultincontinence devices, feminine hygiene articles, medical and surgicalgowns, medical drapes, industrial apparel, building products such as“house-wrap”, roofing components, and the like made using one or more ofthe films disclosed herein. Additionally the films of the presentinvention may also be used in metallized films with a high WVTR,according to the disclosure of U.S. Pat. No. 5,055,338, fullyincorporated herein for purposes of U.S. patent practice.

[0031] High WVTR films, high WVTR film composites, and disposablearticles made therefrom of our invention, are produced from a precursorfilm that is prepared from a polymer composition that comprises at leastone polyolefin component, at least one filler component, and optionallyan elastomeric component. The polyolefin component may be any polyolefinwhich is suitable for film formation such as homo- or co-polymerpolypropylene, homo- or co-polymer polyethylenes or blends thereof Apreferred polyolefin is a copolymer of propylene and low densitypolyethylene, particularly preferred is linear low density polyethylene.The linear low density polyethylene may be a polymer made from eithertraditional Ziegler-Natta or metallocene catalysts, or combinationsthereof.

[0032] In an embodiment of the invention, the films, film composites,and articles made therefrom based on polyolefin filler combinations,when passed through a nip of interdigitating grooved rollers(hereinafter used interchangeably with “ring-rolling”) wouldsurprisingly and unexpectedly have improved water vapor transmissionrates while maintaining resistance to liquid permeability; and retainingfilm integrity. Following is a detailed description of certain preferredfilms, film composites, and/or fabricated disposable articles madetherefrom, within the scope of the present invention. Also disclosed arepreferred methods of producing these films, film composites, andfabricated disposable articles made therefrom as well as preferredapplications thereof. Those skilled in the art will appreciate thatnumerous modifications to these preferred embodiments can be madewithout departing from the scope of the invention. For example: thoughthe properties of certain films, film composites, and fabricatedarticles such as diapers are exemplified, especially after ring-rolling,the films and composites will have numerous other uses. To the extentour description is specific, it is solely for the purpose ofillustrating preferred embodiments of our invention and should not betaken as limiting the present invention to these specific embodiments.

[0033] It will be appreciated by those of ordinary skill in the art thatthe films and film composites of certain embodiments of the presentinvention, can be combined with other polymers or polymer basedfabricated articles such as films, fibers, fabrics (including non-wovenfabrics) and the like, depending on the intended function of theresulting film, film composite or fabricated article.

[0034] As an example of such combinations, by extrusion coating,co-extrusion coating, or by co-extrusion or laminating of the film withother polymer films, e.g. polyolefin, other properties may be achieved.For instance, after ring-rolling an entire film cross-section, certain(machine direction) sections could be extrusion coated to eliminatebreathability in those selected portions so coated. Also contemplatedare varying combinations of the precursor film, or the film afterring-rolling, with other films, or non-woven fabrics, generally madefrom one or more polyolefins. Such combinations, while including theprecursor or the post ring-rolled film, can include severalcombinations, such as non-woven/film, film/non-woven,film/non-woven/film, film/film, and the like.

[0035] Other methods of improving WVTR of a film or article fabricatedfrom the film, may be used in addition to use of the filled polyolefinand process of passing the filled polyolefin film through the nip ofinterdigitating grooved rollers described herein, without departing fromthe intended scope of the invention. For example, including microporousvoids through pin-point punctures (also known as “apertured film”) toimprove the WVTR, in addition to ring-rolling is not excluded by thepresent invention. Also, it is well known that manipulation of a film bychanging quench conditions during melt processing, and/or by irradiatingthe film will have an effect on WVTR and/or physical properties. Suchmechanical or other treatment or manipulation is not excluded by thisinvention.

[0036] Films or film composites employing the polyolefin/filler blendsof certain embodiments of the present invention can be oriented,annealed, or crosslinked Additionally, polyolefin/filler combinations ofthe present invention can be made into film by processes including blownor cast film manufacturing techniques. The blend components can functionto modify barrier, opacity, sealing, cost, or other functions that willbe known to those of ordinary skill in the art.

[0037] The films or composite structures are often used in infantdiapers, toddler training pants, adult incontinence devices, medicaldrapes and apparel, such as surgical gowns, feminine hygiene articles,and the like. Use of the term “film composites” may include one or morefilm and/or non-woven layers bonded mechanically, thermally, oradhesively to the film. Such non-woven materials include spun-bond,meltblown, and combinations thereof

[0038] Such non-woven materials are most often made from polyolefins,such as homopolymer polyethylene, copolymer polyethylene (including oneor more of α-olefins of 4-10 carbon atoms, vinyl acetate, ethylenicallyunsaturated acrylic acid esters, acrylic acid, methacryclic acid,ionomers, polypropylene homopolymers, polypropylene copolymers includingone or more of ethylene and α-olefins of 4-10 carbon atoms, homopolymerand copolymer polypropylene).

Components of A Precursor Film Film Forming Polyolefin

[0039] Most film forming polyolefins and combinations of film formingpolyolefins may be used in embodiments of our invention.

Polyolefin Component

[0040] The polyolefin component can be any film forming polyolefin,including polyethylene and polypropylene and others, or polyolefinblend. Examples of suitable materials are listed in Table 1 below. TABLE1 Suitable Polymers & Relative Benefits Polymer Impact Tear SoftnessDrawdown Metallocene Homo- Preferred Preferred Preferred Most polymersand Copoly- Preferred mers (e.g. Exxon Achieve ™ PD3854) RandomCopolymer More More More More PP (e.g. Exxon PP Preferred PreferredPreferred Preferred 9263) Impact Copolymer Most Most Most Preferredpolypropylene (e.g. Preferred Preferred Preferred Exxon PP 7623)Homopolymer PP Preferred Preferred Preferred Preferred (e.g. Exxon PP1016) Exxon LD 3003 Preferred Preferred Preferred Preferred ElastomerPreferred Preferred Preferred Preferred Plastomer Most Most Most MostPreferred Preferred Preferred Preferred

Polyethylene

[0041] Linear low density polyethylenes are among the materials favoredin embodiments of the invention. Linear low density polyethylene(LLDPE), generally that having density from 0.910 to 0.935 g/cm³ and amelt index from 0.01 to 10 dg/min. Another polyolefin that may beconsidered in such composites is very low density polyethylene (VLDPE,also plastomer) which will have densities in the range of from about0.860 to about 0.910 g/cm³.

[0042] Conventional high pressure low density polyethylene (LDPE) isanother example of a suitable polyethylene which has a density of from0.910 to 0.925 g/cm³

[0043] High density polyethylene (HDPE) having densities in the range offrom about 0.935 to about 0.970 g/cm³ may also be considered. Suchpolyethylenes may be produced by copolymerizing ethylene with one ormore C₄ to C₂₀ α-olefin. Generally the preferred α-olefins include thoseselected from the group consisting of butene- 1, pentene-1,4-methyl-1-pentene, hexene- 1, octene- 1, decene- 1 and combinationsthereof. Most preferred are ethylene copolymers of butene-1, hexene-1,octene-1 and combinations thereof The comonomers may be present inamounts up to 20 mole percent. The amount of comonomer or comonomerswill generally determine density, for instance HDPE will have from 0 to1 mole percent comonomer, while plastomers with densities lower than0.900 g/cm³ will have up to 15 or even 20 mole percent comonomer(s).Such polyethylenes may be made utilizing traditional Ziegler-Natta,chromium based, and metallocene catalysts which may be used withalumoxane and/or ionic activators. Processes useful for preparing suchpolyethylenes include gas phase, slurry, solution and the like. Thedensity of polyethylenes such as these, in preferred embodiments, willgenerally be in the range of from about 0.900 and 0.935 g/cm³,preferably in the range of from about 0.910 to 0.925 g/cm³, mostpreferably from about 0.915 to 0.920 g/cm³. The polyethylenes will havea melt index in the range of from about 0.1 to about 10 g/10 min,preferably 0.5 to 5 g/10 min, generally consistent with film formingconditions.

Polypropylene

[0044] Polypropylene may be used in conjunction with one or morepolyethylenes, or by-itself as the polyolefin component of the precursorfilm. Polypropylene may be made from many of the catalysts and processesdiscussed supra, including optional inclusion of one or more α-olefins.As indicated in Table 1, one of the preferred polymers is a randomcopolymer having low levels, for example up to about 8 wt. %, ofethylene randomly included in a predominantly polypropylene chain.

Elastomer

[0045] One or more elastomers may be included in the polyolefincomponent. Such elastomers include, but are not limited to vulcanizednatural rubber, ethylene alpha olefin rubber (EPM), ethylene alphaolefin diene monomer rubber (EPDM), styrene-isoprene-styrene (SIS),styrene-butadiene-styrene (SBS), styrene-ethylene -butylene-styrene(SEBS), ethylene-propylene (EP), ethylene-vinyl acetate copolymer (EVA),ethylene-maleic anyhydride (EMA), ethylene-acrylic acid (EEA), butylrubber and the like. Of these SIS and SBS are preferred, with SBS moreparticularly preferred. The range of elastomer inclusion are generallyfrom about 1.4 to about 25 wt. %, preferably from about 1.4 to about 20wt. %, and more preferably from about 1.4 to 17.2 wt. %.

[0046] Amounts of each component can vary with the desired propertiesfor the precursor film or film composite. For instance, a nominal 0.917g/cm³ density LLDPE may be combined with 4 wt. % of an elastomer. Such acombination might provide improved elastic behavior.

[0047] Other components in a film forming polyolefin are not excluded.Such components may include additives such as anti-oxidants, anti-staticagents, colors and the like, well known to those of ordinary skill.Further, blending of polyolefins with polymers is also contemplated. Forexample, blending of traditional Ziegler Natta catalyzed (ZN), chromiumcatalyzed (CR), metallocene catalyzed (MCN) and free radical initiated(FR) polyolefins using one or all in a blend as the film formingcomponent is contemplated. For instance including, but not limited toMCN/ZN, MCN/CR, MCN/FR, MCN/ZN/FR, combinations and the like arecontemplated. Other free radical initiated polyethylenes, high pressurepolyethylene, ethylene homopolymers as well as ethylene copolymers maybe included.

[0048] Both in the case of other polyolefins and the elastomericpolymers, the combinations should be generally formable into a film.

[0049] As used in this application, the term “polyolefin” will mean thepolyolefin, any combination of polyolefins, including plastomers,elastomers, additives, and the like.

Film Physical Property Modification

[0050] It was found that the addition of small amounts of low densitypolyethylene, the polyolefin/filler blend allowed film extrusion athigher throughput levels with some majority polymers but with little tono reduction in film breathability. Low density polyethylene with a MeltIndex of 0.9 to 25 (12 MI being preferred), and a density of 0.900 g/cm³to 0.930 g/cm³ may be used.

[0051] Further improvements in film impact and tear strength arepossible by the addition of plastomers, elastomers, styrenic blockco-polymers (SIS, SBS, SEBS), EVA, EMA, EEA, or rubbers. Material gradesincluded are listed in Table 2 below. TABLE 2 Property ImprovementMaterials Supplier Grade Comment 1 Comment 2 Exxon Chemical Exact ™ 3139 7.5 MI Density = 0.900 g/cm³ Exxon Chemical Exact ™ 4044 16.5 MIDensity = 0.895 g/cm³ Exxon Chemical Exact ™ 9095  2.2 MI Density =0.893 g/cm³ Exxon Chemical Exact ™ 3131  3.5 MI Density = 0.900 g/cm³Exxon Chemical Paxox ™  2.0 MI Density = 0.900 g/cm³ SLX 9106 ExxonChemical Paxon ™  3.5 MI Density = 0.900 g/cm³ SLX 9101 Dexco Vector ™4211   13 MI Dexco Vector ™ 4411   40 MI Exxon Vistalon ™ EPDM 3708Exxon Vistalon ™ EPDM 3030 Shell Kraton ™   8 MI SEBS G1657 UnionCarbide UC 9042   5.1 MI Density = 0.900 g/cm³ Union Carbide UC 1085  0.8 MI Density = 0.884 g/cm³

[0052] Filler Materials

[0053] To impart breathability to polyolefin films, addition of fillersand subsequent straining is known.

[0054] To form the precursor film, fillers may be incorporated atrelatively high levels, limited only by the ability of the combination(polyolefin/filler) to be formed into a film. The amount of filler addedto the polyethylene depends on the desired properties of the filmincluding tear strength, WVTR, and stretchability.

[0055] However, it is believed that a film with good WVTR generallycannot be produced as is taught herein with an amount of filler lessthan about 16.5 wt. % of the polyolefin/filler composition. Further, itis believed that useful films may not be made with an amount of thefiller in excess of about 71.5 wt. %. While at lower than about 16.5 wt.% of filler, the polyolefin/filler composition may not have sufficientbreathability. Higher amounts of filler may cause difficulty incompounding and losses in strength of the final breathable film.Generally, the range of filler may be in the range of from about 26 toabout 67 wt. %, preferably in the range of from about 33 to about 60 wt.%. The minimum amount of filler is needed to insure the interconnectionwithin the film of voids created at the situs of the filler,particularly by the stretching operation to be subsequently performed.The preferred filler range is from about 30 to about 70 wt. %, based onthe total weight of the film. More preferred filler loading is fromabout 40 to about 60 wt. %.

[0056] Fillers useful in certain embodiments of the invention may be anyinorganic or organic material or combinations thereof having a lowaffinity for and a significantly lower elasticity than the polyolefincomponent or the optional elastomeric component. Preferably, the fillershould be a rigid material having a non-smooth surface, or a materialwhich is treated to render its surface hydrophobic. The mean averageparticle size of the filler is from about 0.5 to about 7 microns,preferably from about 1 to about 5, more preferably from about 2 toabout 3.5 microns. It should be understood that smaller particle sizes,such as from about 0.75 to 2, will provide the best balance ofcompoundability and eventual breathability, but there relative economicsmakes them generally less useful than particle sizes of 3 microns andabove. Such particle sizes are preferred for films having a thickness offrom about 0.5-6 mils. Examples of the inorganic fillers include calciumcarbonate, talc, clay, kaolin, silica diatomaceous earth, magnesiumcarbonate, barium carbonate, magnesium sulfate, barium sulfate, calciumsulfate, aluminum hydroxide, zinc oxide, magnesium oxide, calcium oxide,magnesium oxide, titanium oxide, alumina, mica, glass powder, zeolite,silica clay, and combinations thereof, and the like. Calcium carbonateis particularly preferred. The inorganic fillers such as calciumcarbonate are preferably surface treated to be hydrophobic so that thefiller can repel water to reduce agglomeration of the filler. Also, thesurface coating should improve binding of the filler to the polymerwhile allowing the filler to be pulled away from the polyolefin when thefilm formed from the polyolefin/filler combination is stretched ororiented. Preferred coatings are stearates, such as calcium stearate,which are generally compliant with FDA regulations. Organic fillers suchas wood powder, pulp powder, and other cellulose type powders may beused. Polymer powders such as Teflon® powder and Kevlar® powder may alsobe included. Combinations of these fillers are also contemplated.

[0057] While a broad range of fillers has been described at a broadrange of inclusion parameters based on weight percentages, otherembodiments are contemplated. For instance, fillers with much higher ormuch lower specific gravity may be included in the polyolefin at amountsoutside the weight ranges disclosed, they will be understood to becontemplated as embodiments of the invention as long as the final film,after orientation has WVTR or drawn down similar to that describedherein. For example, while a preferred filler such as calcium carbonatehas a density of 2.7 g/cm³, other examples of suitable fillers include,without limitation, hollow glass beads (density=0.3 g/cm³), glass fibersor beads (density=1.11 g/cm³) and barium sulfate (density=4.6 g/cm³).

Compounding of the Polyolefin/Filler Composition

[0058] Polyolefin/filler compositions usable in this invention may becompounded in several different ways. The components may be brought intointimate contact by, for example, dry blending these materials and thenpassing the overall composition through a compounding extruder.Alternatively, the polyolefin and filler components may be fed directlyto a mixing device such as a compounding extruder, higher shearcontinuous mixer, two roll mill or an internal mixer such as a Banburymixer Overall, the objective is to obtain a uniform dispersion of thefiller in the polymer without agglomeration, and this is readilyachieved by inducing sufficient shear and heat to cause the polyolefincomponent to melt. However, time and temperature of mixing should becontrolled as is normally done to avoid molecular weight degradation.

Film Extrusion and/or Embossing

[0059] Films contemplated by certain embodiments of the presentinvention may be made utilizing a polyolefin, by processes including,blown, cast, and cast melt embossed, preferred is a cast melt embossedfilm process. In such extrusion processes, the films of the presentinvention can be formed into a single layer film, or may be one layer ormore of a multi-layer film or film composite. Alternatively, thepolyolefin films described in this disclosure can be formed or utilizedin the form of a resin blend where the blend components can function tomodify WVTR, physical properties, draw-down, sealing, cost or otherfunctions. Both blend components and functions provided thereby will beknown to those of ordinary skill in the art. Films of the presentinvention may also be included in laminated structures. As long as afilm, multi-layer film, or laminated structure includes one or morepolyolefin/filler film layers having the WVTR, or draw- down, and thelike of the film, it will be understood to be contemplated as anembodiment of the present invention.

[0060] The film forming composition (polyolefin/polyolefin blends andfiller or fillers) may be manufactured into a precursor film byconventional tubular extrusion (blown bubble process) or by castextrusion. Film formation by cast extrusion may be more convenient, asthe film can be immediately melt embossed as described below.

[0061] In the cast extrusion process, the molten resin is extruded froman elongate die in the form of a web. The web may be pulled over atleast one patterned embossing roller to chill and solidify the film withan embossed pattern for reasons discussed further below. The precursorfilm is may be produced to a gauge of from about 0.5 to 6 mils,preferably from about 0.75 to about 5 mils, more preferably from about 1to about 4 mils, most preferably from about 1.5 to about 3 mils, whichallows for further stretching as described below. However, those ofordinary skill in the art will understand that many factors affect theresponse of the precursor film to the ring-rolling process. It is ourintent that the film or film part of a film composite will havebreathability, and at least a minimum of physical properties to maintainits function, that is the film after ring-rolling (either as part of acomposite or by itself) should have the ability to perform its function.For instance in the side panel of a diaper, the film might even havesubstantial voids, providing excellent breathability, but having enoughstrength to maintain the physical form of the diaper or other articleduring its use.

[0062] The extrusion temperatures, die temperatures, and embossingroller (if used) temperatures will depend on the composition employed,but generally will be in the following ranges for compositions of thepresent invention prepared by cast extrusion: Melt Temperature (° F.)350-550 Die Temperature (° F.) 350-550 Embossing Roller Temperature (°F.)  50-130

[0063] Embossing may be used on the surface of polyolefin films toreduce gloss, although such will not be the films primary function in aring-rolling process. Embossing can be imposed on the precursor filmsurface at the time of the film fabrication for cast extrusion, or at asubsequent time for cast or tubular extrusion by procedures well knownin the art.

[0064] For the present invention, embossing may impose a pattern ofdifferent film thicknesses within the precursor film, and can beconducted with an micro/macro pattern, e.g. cross-hatching, dots, lines,circles, diamonds, hexagons, etc. The pattern can be either in lineand/or off line and the rollers can be engraved with either pin upand/or pin down type configurations.

Use of the Precursor Film

[0065] Traditionally, breathable film has been made using such filmprecursors as described above, and then orienting the film by a varietyof techniques, such as tentering in one or both of the machine direction(MD) or cross or transverse direction (TD). The oriented and breathablefilm could then be used for a variety of end use articles, such asdiapers (usually back sheets, but also top sheets), feminine hygieneitems, bandages, catamenial pads, panty liners, incontinent briefs, andthe like. However, use of certain embodiments of the present inventionwill include the precursor film either by itself or a film composite inan interdigitating grooved roller process. By film composite, we intendthat one or more additional layers or materials are added or laminatedto the film. Such additional materials and layers include syntheticwoven, synthetic non-woven, synthetic knit, non-woven, apertured film,macroscopically expanded three-dimensional formed film, filledcompositions or laminates and/or a combination of these items. Thenon-wovens may be made by processes including, but not limited tospunlace, spunbond, meltblown, carded and or air-through or calendarbonded. The materials or layers of the composite can be combined by manymethod known to those of ordinary skill. For instance, adhesives(including spray adhesives, hot melt adhesives, latex based adhesivesand the like), thermal bonding, ultra-sonic bonding, extrusionlamination, needle punching, and the like. For instance, in themanufacture of infant diapers, toddler training pants, adultincontinence devices, feminine hygiene items, medical gowns, medicaldrapes, and house wrap, parts or all of the final product may beassembled (by for instance heat or adhesive lamination) then the partialor finished construction is passed through one or more pairs ofinterdigitating grooved-rollers to render the precursor film high inWVTR

Stretching

[0066] High WVTR film, film composites or fabricated articles madetherefrom may achieved by stretching the precursor film to forminterconnected voids prior to ring-rolling. Stretching or “orientation”of the film may be carried out monoaxially in the machine direction (MD)or the transverse direction (TD) or in both directions (biaxially)either simultaneously or sequentially using conventional equipment andprocesses following cooling of the precursor film.

[0067] Blown films are preferably stretched in the machine direction orin both directions whereas cast films are preferably stretched in thetransverse direction. For orientation in the MD, the precursor film ispassed around two rollers driven at different surface speeds and finallyto a take up roller. The second driven roller which is closest to thetake up roller is driven faster than the first driven roller. As aconsequence the film is stretched between the driven rollers.

[0068] Stretching of melt embossed precursor films either using both atentering device and a directly in a ring-rolling device or just thering-rolling device produces breathable films having the desired watervapor permeability. The resulting films had greater permeability in theareas of reduced thickness in comparison to the areas of greaterthickness.

[0069] Preferably, the film is stretched through a pair or pairs ofinterdigitating rollers. In this embodiment machine directionorientation is accomplished by stretching the film through a gear likepair of rollers. Transverse direction orientation is accomplished bystretching the film through a pair of disk like rollers. The preferredembodiment employs rollers with a tooth pitch, W=0.080″, however a pitchof 0.040″ to 0.500″ is acceptable. The tooth depth (d), is preferably0.1 00″, however a depth of 0.030″ to 0.500″ is acceptable (see FIG. 4).For the transverse direction orientation rollers, the depth may be up to1″ as mechanical interference is less of an issue with the TD rollers.The preferred embodiment employs interdigitating grooved rollers thatcan be temperature controlled from 50° F. to 210° F., more preferred isa range of from 70° F.-190° F., more preferred is 85° F.-180° F., mostpreferred is 95° F.-1 59° F. Roller temperature may be maintainedthrough internal liquid, electrical systems, an external source ofcooling/heating, combinations thereof, and other methods which will beapparent to those of ordinary skill in the art. The preferred embodimentis internal liquid cooled/heated rollers.

[0070] The depth of engagement of the roller teeth determines the amountof orientation imparted on the film. A balance must be drawn between thedepth of engagement and the level of filler in the film, as manyproperties are affected as depicted in Table 3 below. TABLE 3Relationships Between Process Factors and Resulting Film PropertiesIncreasing Dart Basis CD MD Process Factor WVTR Impact Weight TensileTear CaCO₃ Increase Decrease Decrease MD Increase Decrease DecreaseDecrease Orientation TD Orientation Increase Decrease Decrease DecreaseRoll Increase Decrease Temperature

[0071] Although not thoroughly investigated, controlling of the strainon the film during stretching is believed to be important to controllingthe WVTR. For stretching in the transverse direction, strain iscontrolled for a given stretch ratio by adjusting the film speed and thestretching distance. The stretching distance is measured, between thepoint where the film starts to increase in width to the closest pointwhere the film is fully stretched. For stretching in the machinedirection, strain is controlled for a given stretch ratio by controllingfilm speed and the gap between the first and second driven rollers.

[0072] A range of stretching ratios from 1:2 to 1:5 prove satisfactoryfor MD stretching with a ratio of 1:4 being preferred. A range ofstretching ratios of 1:2 to 1:5 prove satisfactory for TD stretchingwith a ratio of 1:4 being preferred.

[0073] It is a further object of this invention to provide such aprocess for producing a barrier layer having high liquid strikethroughresistance.

[0074] The process of ring-rolling also may activate the elasticity ofthe web (dependent upon specific ring-rolling pattern used), in additionto imparting breathability to the web.

[0075] Precursor webs containing elastomeric components add to theelasticity developed during the ring-rolling process.

Ring-Rolling Process

[0076] To illustrate the process, the term web or webs are used. As usedherein, the term web will include a precursor film and optionally one ormore additional webs or layers, as discussed above, for instance one ormore non-woven webs and/or one or more film webs. Such web componentscan be pre-assembled or laminated. Prior to ring-rolling, at least oneadditional web may be added. Web 10 and alternatively optional web 11may be webs of a precursor film with either another film or fabric (11)the precursor film will have a thickness from 0.5 to 6 mils, Forexample, the optional web 11 may be melt-blown webs of the type taughtin the article entitled “Superfine Thermoplastic Fibers” by Van A.Wente, appearing in Industrial Engineering Chemistry, August, 1956, Vol.48, No. 8 (pages 1342-1346). While melt-blown material may be nylon,polyester, or any polymer or polymer blend capable of being melt-blown,a melt-blown polypropylene web is preferred. A melt-blown web couldcomprise two or more zones of different melt-blown polymers. Melt-blownwebs having a basis weight of up to about 30 g/m² or greater can be usedin the present invention, but lower weight webs are generally preferredin order to minimize the cost of the barrier layer produced therefrom.Technology provides for the production of melt-blown webs with a minimumbasis weight of about 3 g/m², but available commercial melt-blown websgenerally have a basis weight of 10 g/m² or more. The preferred basisweight for optional web 11 is from about 10 g/m² to about 30 g/m²; mostpreferably from about 10 g/m² to about 20 g/m². The density ofmelt-blown optional web 11 is preferably up to about 0.15 g/cm³ and mostpreferably up to about 0.1 g/cm³. Web 10 and optional web 11 may be thesame or different.

[0077] Web 10 and (when present) optional web 11 have preferably beenrolled up together as plies with adjacent surfaces on feed roller 20.They are unrolled from feed roller 20 retaining their contiguousrelationship and passed into the nip of interdigitating grooved rollers24 and 25. Grooved rollers 24 and 25 have grooves perpendicular to theaxis of the rollers (parallel to the machine direction) as shown in FIG.2 which is a sectional view of grooved rollers 24 and 25 taken alongline 2-2 of FIG. 1.

[0078] It has been found that the web 10 and optional web 11 will bestretched more uniformly with less tendency to tear the webs wheninterdigitating grooved rollers 24 and 25 are heated. The rollers arepreferably heated such that their surface temperature are within therange of about 160° F. to 220° F; more preferably within the range of180° F. to 200° F.

[0079]FIG. 1 shows a preferred arrangement of interdigitating groovedrollers 24 and 25 being located with their centers in a horizontal planeand webs 10 and 11 contacting the surface of roll 24 for aboutone-fourth of a revolution before entering the nip between rollers 24and 25; this provides an opportunity for the web or webs 10 and optionalweb 11 to be heated prior to entering the nip. However, interdigitatinggrooved rollers 24 and 25 could be positioned with their centers in avertical plan or at any other angle and web 10 and optional web 11 couldbe fed directly into the nip of the rollers. Preheating of webs 10 and11 if found to be necessary in order to avoid tearing of the webs, couldbe accomplished in any conventional manner. FIG. 4 illustrates how theweb 10 is stretched between the interdigitating grooved rollers 24 and25.

[0080] The webs where two or more webs are fed is stretched and enmeshedwhile passing between the interdigitating grooved rollers 24 and 25 andare thus lightly bonded together producing final product 12. Where finalimproved WVTR composite film 12 has been stretched in the cross-machinedirection by the grooved rollers 24 and 25 of FIGS. 1 and 2, a devicesuch as a curved Mount Hope roll 26 or tenter clamps is needed to extendthe now high WVTR film or film composite to its fullest width. Theextended and smoothed film 12 is then rolled up on a takeup roller 27.

[0081] The amount of lateral stretch imparted to web plies by thegrooved rollers 24 and 25 will depend on the shape and depth of thegrooves of the rollers, and on the gap spacing between the rollers.

[0082] U.S. Pat. No. 4,223,059, issued to Eckhard C. A. Schwarz on Sep.16, 1980 discloses interdigitating rollers having grooves of generallysine-wave shape cross-section which may be used for the presentinvention. U.S. Pat. No. 4,153,664 issued to Rinehardt N. Sabee on May8, 1979, discloses the stretching of polymeric webs by ring-rolling withrollers having grooves with a variety of shapes. The shape of thegrooves of the rollers will generally determine whether the web isstretched uniformly or at incremental, spaced portions of the web.Incremental stretching of the web is more likely to cause some localtearing of film or film composites which would damage the liquidstrikethrough resistance of the film and, therefore, is not preferredfor the present invention.

[0083] A preferred groove pattern for interdigitating rollers 24 and 25is shown in FIG. 3 which is an enlarged view of area 3 of FIG. 2. FIG. 3shows a partial cutaway view of interdigitating rollers 24 and 25. Teeth54 and 55 of grooved roller 24 intermesh with teeth 51, 52 and 53 ofgrooved roller 25. The length 60 of the teeth is 3.81 mm, and thedistance 61 between the centerlines of adjacent teeth on each roller is2.54 mm. The teeth have generally straight sides which are at an angle62 from a plane perpendicular to the axis of rollers 24 and 25 of 9′17″. The land at the base of the teeth has a radius 63 of 0.51 mm. Sharpcorners 66 at the ends of the teeth are removed.

[0084] It is preferred that the interdigitating grooves of rollers 24and 25 be perpendicular to the axis of the rollers. In this way, themaximum number of grooves of a given size will engage the web 10 and 11at the same time and impact stretch to the webs. By having the maximumnumber of teeth engage the web at a given time, a more uniformstretching of the webs is achieved so that local tearing of the film orfilm composite is minimized. The stretched film 12 can be easilysmoothed in the cross-machine direction.

[0085] A reproducible gap setting between grooved rollers 24 and 25 canbe achieved by having the bearing of one of the grooved rollers, e.g.24, stationary while those of the other grooved roller 25 can be movedin the horizontal direction. Grooved roller 25 is moved in thehorizontal direction. Grooved roller 25 is moved toward roll 24 untilits teeth are intermeshed with those of grooved roller 25 and it willmove no further. The bearings of grooved roller 25 are then moved awayfrom grooved roller 24 a measured distance, the gap setting. Thepreferred gap setting for practicing the present invention are fromabout 0.76 mm. to about 1.65 mm. With grooved rollers 24 and 25 having atooth configuration as shown in FIG. 3 and described above, the maximumwidth of film or film composite layer 12 which can be achieved for asingle pass is about 2½ to 3 times the width of starting webs 10 and 11.By incising the gap between grooved rollers 24 and 25, the amount oflateral stretch imparted to webs 10 and 11 is decreased. Therefore, thewidth of film or film composite 12 compared to the width of starting webcan be varied for a single pass between grooved rollers 24 and 25 from amaximum increase of 2½ to 3 times to no increase by the appropriate gapsetting.

[0086] If it is desired to stretch the web more than can be achieved bya single pass between the grooved rollers, multiple passes betweengrooved rollers 24 and 25 can be used.

[0087] Basis weight is generally an important property desired to becontrolled for film or film composite layer (total ring-rolled web) 12.For cost reasons, the lightest film or film composite that will providesufficient breathability is desired. A basis weight of the film producedby itself will be generally above 20 g/cm². The desired basis weight canbe obtained by controlling the amount of stretch imparted to web 10 andoptional web 11 by grooved rollers 24 and 25 as described above, and bythe selection of the basis weights of the starting webs 10 and 11. Forthe present invention, starting webs 10 and 11 have a cumulative basisweight in the range of about 1.1 to 4 times the ultimate desired basisweight, preferably in the range of about 1.5 to 3 times the desiredbasis weight, most preferably about 2 times the desired basis weight.Correspondingly, the desired width of breathable film or film composite12 can be achieved by selecting a proper combination of stretch impartedby the grooved rollers 24 and 25 and initial width of starting webs 10and 11. For the present invention, the initial width of starting webs 10and 11 before passing between grooved rollers 24 and 25 is within therange of about 0.9 to about 0.25 times the desired width, preferablywithin the range of about 0.7 to about 0.3 times the desired width, mostpreferably about 0.5 times the desired width.

Properties of Films Produced WVTR

[0088] In an embodiment of the present invention, certain films andarticles made therefrom have higher WVTR than previously thoughtpossible. The WVTR of such films are greater than 100 g/m²/24 hr @ 37.8°C., 100% RH, preferably greater than 1000, and more preferably greaterthan 2000 g/m²/24 hr ( 37.8° C., 100% RH. Some applications benefit fromfilm with a WVTR at or greater than 10,000 g/m²/24 hr @ 37.8° C., 100%RH.

Test Procedures

[0089] The test procedures used to determine the unique properties ofthe layers of the present invention and to provide the test results inthe examples below are as follows:

Water Vapor Transmission Rate (WVTR)

[0090] Both a Mocon W1, and a Mocon W600 instrument are used to measurewater evaporated from a sealed wet cell at 37.8° C. through the testfilm and into a stream of dry air or nitrogen. It is assumed that therelative humidity on the wet side of the film is approximately 100%, andthe dry side is approximately 0%. The amount of water vapor in the airstream is precisely measured by a pulse modulated infra red (PMIR) cell.Following appropriate purging of residual air, and after reaching asteady state water vapor transmission rate, a reading is taken. WVTR ofthe test films are reported as grams of water/meter²/day. The output ofthe unit is calibrated to the results obtained with a film of knownWVTR. The testing protocols are based on ASTM F1249-90.

Mocon W1

[0091] The Mocon W1 has a single test cell and an analog chart recorder.Air is pumped through a desiccant dryer, then through the test cell, andthen past the PMIR sensor. A 5 minute purge of residual air is followedby a 6 minute test cycle with controlled air flow. The result is asteady state value for WVTR. The purge and test cycles are controlledmanually. The unit is calibrated to a film with a known WVTR every 12hours. Calibration results are control charted and adjustments are madeto the instrument calibration accordingly.

Mocon W600

[0092] The Mocon W600 has 6 measurement cells with PMIR data fed into acomputer. Nitrogen is fed through a desiccant dryer, then through theactive test cell, then past the PMIR sensor. In addition to datacompilation, the computer controls test cycle sequencing. All cells arepurged simultaneously for an 8 minute period. This is followed by an 8minute test cycle for each of the six cells. Total testing time is 56minutes. Two of the test cells always measure reference films with aknown WVTR.

Gurley Porosity

[0093] Teleyn Gurley Model 4190 Porosity Tester with sensitivityattachment is used. The procedure is as follows:

[0094] a) Cut a strip of film (˜2″ wide) across the entire web width,

[0095] b) Insert a film sample to be tested between orifice plates,

[0096] c) Set the sensitivity adjustment on “5”

[0097] d) Turn the inner cylinder so that the timer eye is verticallycentered below the 10 cm³ silver step on the cylinder,

[0098] e) Reset the timer to zero,

[0099] f) Pull the spring clear of the top flange and releasing thecylinder, When the timer stops counting, the test is completed. Thenumber of counts is multiplied by 10 and the resulting number is “Gurleyseconds per 100 cm³”.

[0100] It will be appreciated by those of ordinary skill in the art thatthe films of m-polyethylene resins of certain embodiments of the presentinvention, can be combined with other materials, depending on theintended function of the resulting film.

[0101] Other methods of improving and/or controlling WVTR properties ofthe film or container may be used in addition to the methods describedherein without departing from the intended scope of the invention. Forexample, mechanical treatment such as micro pores.

Liquid Column Strikethrough Resistance Test

[0102] The liquid strikethrough resistance test is a method fordetermining the water pressure in millimeters of water at which waterpenetrates a repellent barrier layer at a specified fill rate and withthe water and barrier layer at a specified temperature. Such a test isdescribed in INDA Journal, Vol. 5, No. 2, Karen K. Leonas; thestrikethrough resistance of embodiments of the invention are from 50-500cm.

[0103] The following non-limiting examples are provided for illustrativepurposes only.

EXAMPLES Examples 1-12

[0104] LLDPE/CaCO₃ films are made utilizing the following conditions,materials and equipment shown in Table 4.

[0105] Examples 1-12 used LL-3003.09 (a 3 MI, 0.917 g/cm³ polyethylene(Z-N) available from Exxon Chemical Co., Houston, Tex.) containinglevels of CaCO₃ as shown in Table 4, blended with 100 parts of LL-3003.

Examples 13-16

[0106] Example 13-16 were made under the conditions shown in Table 4,Examples 1-12, but with Exceed® ECD-112 (a 3.4 MI, 0.917 g/cm³ densitym-LLDPE from Exxon Chemical Co., Houston, Tex.) with filler, masterbatch (MB) and elastomer levels as shown in Table 5.

[0107] Examples 1-4, 9, 10, 11, 12, 13, 14 and 15 were run on a DavisStandard cast line. Examples 9, 10, 11, 12, 14, and 15 were oriented inthe TD, Example 9, 10, 11, 12, and 15 were further MD drawn. Examples 5,6, 7, 8, and 16 were run on a blown film extruder.

[0108] Each film sample was run through various ring-rolling apparatusas shown in Tables 5, 6 and 7, with the results for basis weight shownin Table 5, the results for WVTR in Table 6, the results for airporosity shown in Table 7. TABLE 4 Condition Example 1 Example 2 Example3 Example 4 Example 5 Example 6 Example 7 Example 8 Material A B B B C DE F Process Cast/TD Cast Cast Cast Blown Blown Blown Blown Ext. RPM 17 68 11 45 65 65 61 Screen PSI 2600 2150 2380 2800 5290 6000 5730 6300 DiePSI 940 750 810 900 N/A/ N/A N/A N/A Melt Temp 390 374 378 388 400 410411 430 Up Width 23 28 28 28 9 11 11 11 Down Width 62.4 N/A N/A N/A N/AN/A N/A N/A FPM 165 65 77 102 30 28 30 28 MD Drawn N/A N/A N/A N/A N/AN/A N/A N/A Example Example Example Example Example Example ExampleCondition Example 9 10 11 12 13 14 15 16 Material G B H B B B B EProcess Cast/TD/ Cast/TD/ Cast/TD/ Cast/TD/ Cast Cast/TD Cast/TD/ BlownMD/Drawn MD Drawn MD Drawn MD Drawn MD Drawn Ext. RPM 15 21 15 22 19 1919 35 Screen PSI 3600 3440 3138 3302 3740 3740 3740 4750 Die PSI N/A N/AN/A N/A 1270 1270 1270 N/A Melt Temp 414 402 390 350 430 430 430 425 UpWidth 21 21 21 24 22 22 22 10 Down Width 83 77 82 89 N/A 63 63 N/A FPM181 195 186 140 340 340 340 25 MD Drawn 1:3 1:3 1:3 1:3 N/A N/A 1:3 N/AMaterial LLDPE CaCO₃ EVA SBS A 63% 37% B 50% 50% C 40% 40%  8% 12% D 35%35% 12% 18% E 30% 30% 16% 24% F 40% 40% 20% G 55% 45% H 53% 47%

[0109] TABLE 5 BASIS WEIGHT (Grams/Square Meter) PROPERTIES BEFOREACTIVATION PROPERTIES AFTER ACTIVATION Type 1 Type 2 Type 3 Type 4 Type5 Mat. Mfg. Weight Air Porosity Manual Ring-Roll Ring-Roll Ring-RollTooth Example Comp.** Meth.* g/m² WVTR sec/100 cm³ Stretch 0.400 DOE0.175 DOE 0.100 DOE Pattern 1 A AA 22 1318 >10000 Destroyed Destroyed 21N/A 2 B BB 79 <100 N/A 23 N/A N/A N/A 3 B BB 86 <100 N/A 25 N/A N/A N/A4 B BB 108 <100 N/A 29 N/A N/A N/A 5 C CC 53 <100 N/A N/A N/A 6 D CC<100 N/A N/A N/A 7 E CC 49 <100 N/A 21 N/A N/A 8 F CC 54 <100 N/A N/AN/A 9 G DD 18 8000 190 Destroyed N/A N/A 10 B DD 25 7000 300 DestroyedN/A N/A 11 H DD 20 6100 642 Destroyed N/A N/A 12 B DD 36 7100 898Destroyed N/A N/A 13 B BB 73 <100 N/A 29 14 B AA 23 7900 210 15 B DD 218000 263 22 16 B CC 22 <100 N/A 11 *Compositions of Raw Materials LLDPECaCO₃ EVA SBS **Manufacturing Methods A 63% 37% AA CAST/TD B 50% 50% BBCAST C 40% 40%  8% 12% CC BLOWN D 35% 35% 12% 18% DD CAST/TD/MD DRAWN E30% 30% 16% 24% F 40% 40% 20% G 55% 45% H 53% 47%

[0110] TABLE 6 WATER VAPOR TRANSMISSION RATE (g/square meter/24 hours)BASIS WEIGHT (Grams/Square Meter) PROPERTIES BEFORE ACTIVATIONPROPERTIES AFTER ACTIVATION Type 1 Type 2 Type 3 Type 4 Type 5 Mat. Mfg.Weight Air Porosity Manual Ring-Roll Ring-Roll Ring-Roll Tooth ExampleComp.** Meth.* g/m² WVTR sec/100 cm³ Stretch 0.400 DOE 0.175 DOE 0.100DOE Pattern 1 A AA 22 1318 >10000 Destroyed Destroyed 750 N/A 2 B BB 79<100 N/A 1300 N/A N/A N/A 3 B BB 86 <100 N/A 1300 N/A N/A N/A 4 B BB 108<100 N/A 1600 1100 N/A N/A N/A 5 C CC 53 <100 N/A 400 360 N/A N/A 800 6D CC <100 N/A 200 350 N/A N/A 400 7 E CC 49 <100 N/A 200 290 N/A N/A 2008 F CC 54 <100 N/A 200 240 N/A N/A 450 9 G DD 18 8000 190 Destroyed 7100N/A N/A 10 B DD 25 7000 300 Destroyed 9200 N/A N/A 11 H DD 20 6100 642Destroyed 9000 N/A N/A 12 B DD 36 7100 898 6900 Destroyed 7850 N/A N/A13 B BB 73 <100 N/A 1400 14 B AA 23 7900 210 6400 15 B DD 21 8000 2637350 16 B CC 22 <100 N/A 2600 *Compositions of Raw Materials LLDPE CaCO₃EVA SBS **Manufacturing Methods A 63% 37% AA CAST/TD A 63% 37% BB CAST B50% 50% CC BLOWN C 40% 40%  8% 12% DD CAST/TD/MD DRAWN D 35% 35% 12% 18%E 30% 30% 16% 24% F 40% 40% 20% G 55% 45% H 53% 47%

[0111] TABLE 7 AIR POROSITY (Seconds/100 cm³/Square inch) BASIS WEIGHT(Grams/Square Meter) PROPERTIES BEFORE ACTIVATION PROPERTIES AFTERACTIVATION Type 1 Type 2 Type 3 Type 4 Type 5 Mat. Mfg. Weight AirPorosity Manual Ring-Roll Ring-Roll Ring-Roll Tooth Example Comp.**Meth.* g/m² WVTR sec/100 cm³ Stretch 0.400 DOE 0.175 DOE 0.100 DOEPattern 1 A AA 22 1318 >10000 Destroyed Destroyed >10000 N/A 2 B BB 79<100 N/A 4165 N/A N/A N/A 3 B BB 86 <100 N/A 9966 N/A N/A N/A 4 B BB 108<100 N/A 5685 N/A N/A N/A 5 C CC 53 <100 N/A >10000 N/A N/A 890 6 D CC<100 N/A >10000 N/A N/A 6320 7 E CC 49 <100 N/A >10000 N/A N/A >10000 8F CC 54 <100 N/A >10000 N/A N/A 640 9 G DD 18 8000 190 Destroyed 33 N/AN/A 10 B DD 25 7000 300 Destroyed 48 N/A N/A 11 H DD 20 6100 642Destroyed  5 N/A N/A 12 B DD 36 7100 898 Destroyed 17 N/A N/A 13 B BB 73<100 N/A 14 B AA 23 7900 210 15 B DD 21 8000 263 258 16 B CC 22 <100 N/A*Compositions of Raw Materials LLDPE CaCO₃ EVA SBS **ManufacturingMethods A 63% 37% AA CAST/TD A 63% 37% BB CAST B 50% 50% CC BLOWN C 40%40%  8% 12% DD CAST/TO/MD DRAWN D 35% 35% 12% 18% E 30% 30% 16% 24% F40% 40% 20% G 55% 45% H 53% 47%

Example 17

[0112] A blend of 57% ECC FilmLink 400 CaCO₃ was combined with 33% ExxonPD 7623 Impact Copolymer, 2% Exxon LD-200.48, and 8% Exxon Exact 313 1oriented in interdigitating rollers of 0.080″ pitch. The MD depth ofengagement was 0.020″, and the TD depth of engagement was 0.040″. Thetemperature of the interdigitating grooved rollers was 140° F.

Example 18

[0113] A blend of 57% ECC FilmLink 400 CaCO₃ was combined with 33% ExxonPD 7623 Impact Copolymer, 2% Exxon LD-200.48, and 8% Exxon Exact 3131oriented in interdigitating rollers of 0.080″ pitch. The MD depth ofengagement was 0.020″, and the TD depth of engagement was 0.040″. Thetemperature of the interdigitating grooved rollers was 110° F.

Example 19

[0114] A blend of 57% ECC FilmLink 400 CaCO₃ was combined with 33% ExxonPD 7623 Impact Copolymer, 2% Exxon LD-200.48, and 8% Exxon Exact 3131oriented in interdigitating rollers of 0.080″ pitch. The MD depth ofengagement was 0.020″, and the TD depth of engagement was 0.040″. Thetemperature of the interdigitating grooved rollers was 70° F.

[0115] As can be seen from Table 8, the WVTR rise from a rollertemperature of 70° F (considered ambient temperature) to 110° F. then140° F. is dramatic, unexpected and surprising. It would be expectedthat heating the film would soften it and the polymer would not tearaway from the filler as easily. Such a result would likely cause feweror smaller pores, and thereby reduced WVTR. Accordingly, the significantincrease in WVTR produced by using heated rollers is both surprising andunexpected. TABLE 8 Example 17 Example 18 Example 19 Roller Temperature(° F.) 140 110  70 Basis Weight (g/m²)  43  40  39 WVTR (g/m²/day) 4100 3000  1900  Dart Impact (g) 240 300 300 MD Ultimate (g/in) 1585  1532 1453  MD Elongation (%) 408 431 442 TD @ 5% (g/in) 457 389 388 TDUltimate (g/in) 785 1166  1049  TD Elongation (%) 351 358 357 MDElmendorf Tear (g) 166 208 205

[0116] A linear regression analysis reveals that with the above fixedformulation, depth of activation water vapor transmission rate ispredicted by the following equation:

WVTR=−329.73+31.2162* Roller Temperature (° F.)

Example 20

[0117] A blend of 52% ECC FilmLink 400 CaCO₃ was combined with 48% ExxonPD 7623 Impact Copolymer Polypropylene. Film was oriented off line withinterdigitating rolls of 0.100″ pitch. The MD depth of engagement was 0.030″ and the TD depth of engagement was 0.019″.

Example 21

[0118] A blend of 52% ECC FilmLink 400 CaCO₃ was combined with 40% ExxonPD 7623 Impact Copolymer, 2% Exxon LD-202.48, and 6% Exxon SLX9101. Filmwas oriented in interdigitating rolls of 0.080″ pitch. The MD depth ofengagement was 0.028″, and the TD depth of engagement was 0.034″.

Example 22

[0119] A blend of 55% ECC FilmLink 400 CaCO₃ was combined with 31% ExxonPD 7623 Impact Copolymer, 4% Exxon LD-202.48, 2% Ampacet 110131 TiO₂concentrate, and 8% Exxon Exact 313 1. Film was oriented ininterdigitating rolls of 0.080″ pitch. The MD depth of engagement was0.021″, and the TD depth of engagement was 0.037″.

[0120] Table 9 demonstrates the high absolute values of tear and impactstrenght relative to known polypropylene breathable films. Also shown isthe further property improvement made by the addition of minorityamounts of other polyolefins. TABLE 9 Film Properties Example 20 Example21 Example 22 Basis Weight (g/m²) 41.0 40.6 40.3 WVTR (g/m²/day) 14571462 1400 Dart Impact (g) 210 315 315 MD Ultimate (g/cm) 625 609 604 MDElongation (%) 423 482 448 TD @ 5% (g/cm) 231 151 140 TD Ultimate (g/cm)367 501 440 TD Elongation (%) 410 464 398 Light Transmission (%) 45 4339 MD Elmendorf Tear (g) 79 195 198

[0121] While the present invention has been described and illustrated byreference to particular embodiments thereof, it will be appreciated bythose of ordinary skill in the art that the invention lends itself tovariations not necessarily illustrated herein. For example, it is notbeyond the scope of this invention to include additives with the claimedimproved, high WVTR film process. For this reason, then, referenceshould be made to the appended claims and the remainder of thespecification for purposes of determining the true scope of the presentinvention.

We claim:
 1. A process for producing a film having a WVTR greater than200 g/m²/day at 38° C. and 90% relative humidity comprising a polyolefinand a filler, said process comprising: a) extruding a precursor filmfrom said polyolefin blend comprising said first and said second polymercompositions and said filler, said filler concentration being in a rangeof from about 16.5 to about 71.5 wt. %; and b) passing said precursorfilm between at least one pair of interdigitating grooved rollers, saidrollers being maintained in a temperature range of from about 91° F. toabout 159° F., so that said film is heated to produce said film having aWVTR greater than 200 g/m²/day at 38 ° C. and 90% relative humidity. 2.The process of claim 1 wherein said polyolefin is selected from thegroup consisting of polypropylene, polyethylene, ethylene polarcomonomer polymers, ethylene α-olefin copolymers and combinationsthereof.
 3. The process of claim 1 further comprising cooling saidprecursor film to a temperature of at least 75° F. or less after step a)but prior to step b).
 4. The process of claim 1 wherein said rollers aremaintained in a temperature range of from about 95° F. to about 159° F.5. A process for producing a film having a WVTR of at least 200 g/m²/dayat 38° C. and 90% relative humidity comprising a polyolefin blend, saidpolyolefin blend having at least a first and a second polymercomposition, and a filler, said process comprising: a) extruding aprecursor film from said polyolefin blend comprising said first and saidsecond polymer compositions and said filler, said filler concentrationbeing in a range of from about 16.5 to about 71.5 wt. %, wherein, i)said first polymer composition is a polypropylene and ii) said secondpolymer composition is selected from the group consisting of elastomers,plastomers, styrenic block copolymers, ethylene-maleic anhydridecopolymers, ethylene ethyl acetate, and combinations thereof, and b)passing said precursor film between at least one pair of interdigitatinggrooved rollers so that said film has at least i) a WVTR in a range offrom about 200 g/m²/day to about 10,000 g/m²/day at 38° C. and 90%relative humidity, ii) a dart drop impact in a range of from about 100grams to about 300 grams, and iii) an elongation selected from the groupconsisting of machine direction, transverse direction and combinationsthereof in a range of from about 150% to about 550%.
 6. The process ofclaim 5 wherein said polypropylene is selected from the group consistingof random copolymer polypropylene, impact copolymer polypropylene,polypropylene produced with a metallocene catalyst and combinationsthereof.
 7. The process of claim 5 wherein said elastomer is selectedfrom the group consisting of styrene-isoprene-styrene,styrene-butadiene-styrene, styrene-ethylene -butylene-styrene, ethylenealpha-olefin rubber, ethylene propylene diene monomer rubber, butylrubber, vulcanized natural rubber and combinations thereof.
 8. Theprocess of claim 5 wherein said plastomer is at least one ethyleneα-olefin copolymer selected from the group consisting of ethyleneα-olefin copolymers wherein the α-olefin comonomer is selected from thegroup consisting butene, pentene, hexene, and combinations thereof. 9.The process of claim 5 wherein a non-woven polymeric material islaminated to said precursor film, after step a) but prior to step b),using a lamination means selected from the group consisting of adhesive,heat, ultrasonic radiation and combinations thereof.
 10. The process ofclaim 5 wherein said interdigitating grooved rollers are positioned in adirection selected from the group consisting of machine direction,transverse direction and combinations thereof.
 11. The process of claim5 further comprising forming said film of step b) into a fabricatedarticle selected from the group consisting of diapers, adultincontinence devices, surgical apparel, surgical drapes, sports apparel,industrial apparel, house wrap, filtration media and controlledatmosphere packaging.